怎么这个select语句会select出两条相同的记录

select c.callid_master,do.id, c.start_Time, c.ani, c.calling_Device, c.callee_Device, c.answer_Duration,
c.call_Type, c.ani_Area FROM Call_Master as c, Device_Info do
WHERE c.answer_Duration=0 AND c.call_Type in (1,3)
AND do.device = c.callee_Device and ((do.device =8760))
order by c.start_Time